Butomus umbellatus

Butomus

Butomus is the sole genus in the monogenetic plant family Butomaceae, containing the single species Butomus umbellatus, also known as flowering rush or grass rush.

Description

The plant is a rhizomatous perennial aquatic plant. Its name is derived from Greek bous, meaning "cow", "ox" etc and tome, a cut (the verb 'temnein' meaning "to cut"), which refers to the plant's swordlike leaves.

Other than suggested by its English common name, it is not a true rush. It is native to Eurasia and grows on the margins of still and slowly moving water down to a depth of about 3 m. It has pink flowers. Introduced into North America as an ornamental plant it has now become a serious invasive weed in the Great Lakes area. In Israel, one of its native countries, it is an endangered species due to the dwindling of its habitat.

The plant has linear leaves up to 1 metre long, or more. The leaves are triangular in cross-section and arise in two rows along the rhizome.

The inflorescence is umbel-like consisting of a single terminal flower surrounded by three cymes. The flowers are regular and bisexual. There are three petal-like sepals which are pink with darker veins. They persist in the fruit. The three petals are like the sepals but somewhat larger. 6 - 9 stamens. Carpels superior, 6 - 9 and slightly united at the base. When ripe they are obovoid and crowned with a persistent style. Ovules are numerous and found scattered over the inner surface of the carpel wall, except on the midrib and edges. Fruit is a follicle. The seeds have no endosperm and a straight embryo.

Butomaceae

Butomaceae has been recognized by most taxonomists as a plant family; it is sometimes called the "flowering-rush family".

The APG II system, of 2003 (unchanged from the APG system, 1998), also recognizes such a family, and places it in the order Alismatales, in the clade monocots. The family counts a single species, Butomus umbellatus.

At the ranks of family and order this is the same placement as in the Cronquist system. However, Cronquist assumed a much smaller order and assigned the order to subclass Alismatidae, in class Liliopsida [=monocotyledons].

Uses

Frequently cultivated as an attractive ornamental plant. In parts of Russia the rhizomes are used as food.

External links

The species

The family

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